Lithium-ion battery

ABSTRACT

A lithium-ion battery having an anode including an array of nanowires electrochemically coated with a polymer electrolyte, and surrounded by a cathode matrix, forming thereby interpenetrating electrodes, wherein the diffusion length of the Li +  ions is significantly decreased, leading to faster charging/discharging, greater reversibility, and longer battery lifetime, is described. The battery design is applicable to a variety of battery materials. Methods for directly electrodepositing Cu 2 Sb from aqueous solutions at room temperature using citric acid as a complexing agent to form an array of nanowires for the anode, are also described. Conformal coating of poly-[Zn(4-vinyl-4′ methyl-2,2′-bipyridine) 3 ](PF 6 ) 2  by electroreductive polymerization onto films and high-aspect ratio nanowire arrays for a solid-state electrolyte is also described, as is reductive electropolymerization of a variety of vinyl monomers, such as those containing the acrylate functional group. Such materials display limited electronic conductivity but significant lithium ion conductivity. Cathode materials may include oxides, such as lithium cobalt oxide, lithium magnesium oxide, or lithium tin oxide, as examples, or phosphates, such as LiFePO 4 , as an example.

RELATED CASES

The present application claims the benefit of provisional patentapplications: (a) Ser. No. 61/030,868 for “Electrodeposition of Cu₂SbFor Li-Ion Batteries From Aqueous Solution At Ambient Conditions” by AmyL. Prieto et al., filed on 22 Feb. 2008; (b) Ser. No. 61/083,764 for“Three-Dimensional Lithium-Ion Battery With Nanoscale Dimensions” by AmyL. Prieto et al., filed on 25 Jul. 2008; (c) Ser. No. 61/111,268 for“Conformal Coating Of Nanowire Arrays Via ElectroreductivePolymerization” by Amy L. Prieto et al., filed on 4 Nov. 2008; and (d)Ser. No. 61/116,162 for “Electrochemically Reduced Lithium-IonConducting Polymer Films Of Acrylates” by Amy L. Prieto et al., filed on19 Nov. 2008, which provisional applications are hereby incorporated byreference herein for all that they disclose and teach.

STATEMENT REGARDING FEDERAL RIGHTS

This invention was made with government support under Contract No.ECS0709412 awarded by the National Science Foundation to Colorado StateUniversity. The government has certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates generally to batteries and, moreparticularly to lithium-ion batteries.

BACKGROUND OF THE INVENTION

Lithium is the lightest and most electropositive element, making itwell-suited for applications that require high energy density. As such,lithium-ion (Li⁺) batteries have been successfully employed in a largevariety of portable and other electronic devices. However, slowdiffusion of Li⁺ into the anode and the cathode, as well as slowdiffusion between the two electrodes, remain the two principallimitations to the rates of charging and discharging for thesebatteries.

Nanostructured materials have been demonstrated to be useful for Li⁺batteries due to their high surface area-to-volume ratio, a propertythat has been shown to lead to greater reversibility for the lithiationreaction and greater discharge rates. Moreover, fabrication of nanowirearrays of both carbon-based anodes and several common cathode materialshas been shown to enhance electrode performance because the reduction inparticle size of the electrode materials, while maintaining electricalcontact from grain to grain, reduces the distances the Li⁺ ions mustdiffuse.

In particular, the charge/discharge rate of a battery is related to therates of diffusion of Li⁺ into each electrode and the rate of diffusionbetween the cathode and the anode. While nanowires have been shown tocycle faster than bulk materials, reducing the distance between cathodeand anode battery structures has not been straightforward, and althoughnanostructured cathodes/anodes have previously been utilized in Li⁺batteries, this was done primarily to increase the surfacearea-to-volume ratio of either the cathode or anode or both, and the Li⁺diffusion distance remained, as a consequence, quite large as lithiumions were required to travel large distances between macroscopicallyseparated electrodes.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide alithium-ion battery effective for increasing the diffusion rate of Li⁺between the battery anode and cathode.

Another object of the invention is to provide a lithium-ion batteryeffective for increasing the rate of diffusion of Li⁺ into the batteryanode and cathode.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

To achieve the foregoing and other objects, and in accordance with thepurposes of the present invention, as embodied and broadly describedherein, the lithium-ion battery, hereof, includes in combination: ananode including electrodeposited structures having intermetalliccomposition effective for reversibly intercalating lithium ions, thestructures being in electrical communication with a first electrode; alithium-ion conducting solid-state electrolyte deposited on thestructures of the anode; and a cathode material interpenetrating thespace between the structures of the anode in electrical communicationwith a second electrode.

In another aspect of the invention, and in accordance with its objectsand purposes, the method for producing a lithium-ion battery, hereof,including the steps of: forming an anode comprising electrodepositedstructures having intermetallic composition effective for reversiblyintercalating lithium ions, the structures being in electricalcommunication with a first electrode; depositing a lithium-ionconducting solid-state electrolyte on the structures of the anode; andinterpenetrating the space between the structures of the anode with acathode material in electrical communication with a second electrode.

In still another aspect of the invention, and in accordance with itsobjects and purposes, an electrode including electrodeposited structureshaving intermetallic composition.

Benefits and advantages of the present invention include, but are notlimited to, providing a battery having nanoscale dimensions wherein theelectrodes are interpenetrating, thereby significantly reducing thedistance which the Li⁺ ions are required to traverse uponcharging/discharging of the battery over other types of lithium-ionbatteries.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the embodiments of the present inventionand, together with the description, serve to explain the principles ofthe invention. In the drawings:

FIGS. 1A-1C illustrate a method for assembling the battery of thepresent invention, wherein the step of generating an anode including anarray of conducting structures in electrical contact with a conductingsubstrate is shown in FIG. 1A; FIG. 1B shows the step of placing aconformal coating of an electrolyte material onto the conductingstructures shown in FIG. 1A hereof; and the step of interpenetratingcathode material between the anode structures in electrical connectionwith a second conductive substrate is shown in FIG. 1C.

FIG. 2 illustrates a sample square wave effective for the pulsedelectrodeposition of Cu₂Sb wires, where the deposition potential (E_(f))was the same potential as used in the electrodeposition of Cu₂Sb films(−1.05 V versus SSCE).

DETAILED DESCRIPTION OF THE INVENTION

Briefly, the present invention includes a lithium-ion (Li⁺) batteryhaving an anode comprising an array of nanowires electrochemicallycoated with a polymer electrolyte, and surrounded by, and in electricalcommunication with a cathode matrix, forming thereby interpenetratingelectrodes, and a method for producing such batteries. The presentbattery architecture increases the diffusion rates of the Li⁺ betweenthe cathode and anode by reducing the Li⁺ diffusion length between thesetwo electrodes. Small, lightweight batteries having long lifetimes, andcapable of rapidly discharging power may be constructed.

In accordance with embodiments the present invention, an array of highaspect-ratio nanostructures (such as nanowires, nanoribbons, nanotubes,and nanocones, as examples) having dimensions (for example, length) suchthat one dimension may be 10 to 1000 times larger than a smallerdimension (for example, the diameter of a wire) which may havenanometer-scale dimensions, may be formed on conductive, generallyplanar substrates. Nanorods, having an aspect ratio of less than 10 mayalso be formed. In what follows the term “nanowire” will be utilized asexemplary of “nanostructures.”

Dendritic growth of metallic lithium onto the commonly used graphiteanodes can lead to shorting in the battery and may cause safety issues.Therefore, new anode materials and morphologies are desired in whichthese safety issues, as well as the capacity and the charge/dischargerates, can be improved over graphite. Intermetallic compounds offer thepossibility of improved capacity, a highly reversible reaction withlithium, and a lithium intercalation potential that may be less negativethan the deposition potential of metallic lithium, the latter propertybeing useful for eliminating dendritic growth of elemental lithium onthe electrode. A drawback of using intermetallics as anode materials hasbeen the irreversible loss in capacity during cycling due to largevolume changes which result in pulverization of the electrode duringcycling and, consequently, a loss of electrical contact between theanode and the remainder of the battery. Cu₂Sb is an intermetalliccomposition that does not exhibit large volume changes during thecharging and discharging. Another benefit of Cu₂Sb is that its operatingpotential precludes lithium metal plating. The use of Cu₂Sb nanowireshas an additional benefit in that electrodes having nanoscale dimensionsgenerally provide immunity from pulverization resulting from largevolume changes, even over electrodes having micron scale dimensions.

As will be described hereinbelow, Cu₂Sb may be directly deposited onto aconducting substrate with precise control of composition and thicknessunder mild conditions, and onto complex shapes and into deep recesseswith excellent electrical contact without requiring post-annealing.Codeposition of Cu and Sb from aqueous solutions presents twochallenges: the reduction potentials of Cu and Sb differ byapproximately 130 mV in aqueous solutions, and the deposition of Cu ispreferred at less negative potentials; and while antimony salts aresoluble in acidic solutions, they precipitate in neutral aqueoussolutions to form Sb₂O₃. The electrodeposition of Sb is not possible inacidic solutions because H₂ is formed from the reduction of H₂O, at lessnegative potentials than those required to reduce Sb³⁺. Citric acid(C₆H₈O₇) may be used to keep Sb³⁺ in solution in less acidic solutionsand/or shift its reduction potential to less negative potentials. Citricacid has been used as a complexing agent in deposition solutions forcopper and antimony separately, due to its three carboxylic acid groupsand one hydroxyl group. The resulting complexation of the Sb³⁺ by thecitrate species in solution allows the pH to be raised without theformation of Sb₂O₃, and results in a widening of the electrochemicalwindow of the solution and shifted toward more negative potentials.

The direct electrodeposition of the intermetallic composition, Cu₂Sb,from aqueous solutions containing the required stoichiometric amount ofcopper versus antimony (for Cu₂Sb) has been achieved using citric acidas a complexing agent, thereby increasing the solubility of antimonysalts and shifting the reduction potentials of copper and antimonytoward each other, and enabling the direct deposition of theintermetallic compound at room temperatures and at a pH=6. Theelectrodeposition was performed onto copper substrates resulting in aCu₂Sb thin film that is homogeneous, stoichiometric and crystalline.

One embodiment of the present method utilizes anodic aluminum oxide(AAO) technology to form an array of channels in the alumina substrate.Cu₂Sb is deposited into the nanochannels at a single electrochemicalpotential. The intermetallic compound, Cu₂Sb, displays excellentproperties for use as an anode in Li⁺ batteries: (a) increased chargestorage capacity; (b) increased charging and discharging rates; and (c)reduced hazard of plating lithium metal onto the anode. Otherintermetallic compounds also display these properties and may functionequally well as anodes. Once a suitable anode material is deposited intothe nanochannels, the AAO template is removed using standard chemicaltechniques. The remaining array of nanostructures (Cu₂Sb nanowires, inthe present case) functions as a nanostructured anode having a highsurface area. The nanostructures generated may display a high aspectratio, generally having dimensions on the order of a few nanometers toseveral hundred nanometers in diameter and tens of nanometers to severalhundred micrometers in length.

An electrically-insulating polymer may then be deposited onto the anode,conformally coating the nanowires and serving as the batteryelectrolyte. The electrolyte's function is to allow passage of Li⁺ whileoffering a high resistance to electrical conduction (i.e., the passageof electrons or electrical current). Although any insulating materialcapable of conducting Li⁺ is suitable, it should be applied in agenerally conformal manner as a very thin layer which does notsignificantly modify the nanowire shapes within the array. One exampleis an electrochemically deposited poly(pyridine)zinc polymer preparedfrom [tris(4-methyl-4′-vinyl-2,2′-bipyridine)Zn](PF₆)₂) using areduction technique, although other insulating polymers could bedeposited electrochemically or otherwise by procedures known to thoseskilled in the art (including polyethylene carbonate derivatives). Thethickness and material of the electrolyte is chosen such that theelectrolyte is substantially electrically insulating but the nanowireshape is not substantially distorted. An insulating material, which maybe the same material as that used for the conformal electrolyte coating,but may be any other electrically insulating material, covers exposedsurfaces of the planar conductive substrate. Typically, the thickness ofthe electrolyte may be between about one nanometer and about a fewhundred nanometers.

A cathode material may be introduced such that the coated nanowires inthe array are further covered, and electrical contact made with a secondelectrode. Any suitable Li⁺ battery cathode material may be used withLiCoO₂, LiMnO₂, and Li₂SnO₃, or phosphates, as examples. Such materialsmay be deposited in a number of ways. A sol-gel method, to be describedhereinbelow, permits uniform distribution of the cathode material intothe coated nanowire array.

Intermetallic materials having similar crystal structures to theirlithiated counterparts have been sought since, with both the parent andproduct crystal structure being similar, less rearrangement is neededduring the charging and discharging of the material, thereby reducingthe volume change. Copper antimonide is one such intermetallic, with theantimony atoms in a face center cubic array in both the parent andproduct crystal structures. The similarity in crystal structures leadsto an overall volume change of 95% upon lithiating Cu₂Sb to Li₃Sb(compared to 300% for Sn). The improvement in cycle life of Cu₂Sb hasbeen demonstrated, maintaining a capacity of 1914 mAh ml⁻¹ after 35cycles. Further, nanowires of Cu₂Sb should be less prone to degradationduring charging and discharging than graphite, because of the inherentproperties of the material and the nanoscale dimensions of the wires.

Previous investigations into the battery performance of Cu₂Sb involvedusing slurries of the active material mixed with a binder and carbonblack since the binder is used to attach the powder to an electrode,thereby making electrical contact, and allows the material to undergosignificant volume change without losing electrical contact with thecurrent collector. To reproduce this soft matrix, a thin layer ofgraphite was evaporated onto a copper substrate, and then Cu₂Sb waselectrodeposited onto the graphite. The graphite acted as a “soft”interface, which accommodates the volume change of the Cu₂Sb whilekeeping the electrical contact to the substrate. A steady capacity of200 mAhg⁻¹ was maintained, whereas in the case of Cu₂Sb on Cu thecapacity falls dramatically during the first few cycles until it reachesa minimum of 24 mAhg⁻¹. The graphite was found to improve the reversiblecapacity by an order of magnitude. Cycling capacity was alsoinvestigated as a function of film thickness. As the film gets thinner,the capacity of the film has been found to be maintained for a greaternumber of cycles. Nanowires of Cu₂Sb are expected to have an evengreater ability to maintain capacity upon repeated cycling since themicron thickness of the prepared films is greater than the radius of thenanowires. Moreover, strain due to volume changes is better accommodatedin a nanowire where it is constrained only in the longitudinaldirection, than in a film where the material is constrained in all threedimensions. Thus, electrode material degradation in lithium-ionbatteries may be reduced by using nanoscale morphology since materialshaving small dimensions survive longer than bulk materials.

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. In the Figures, similar structure will be identified usingidentical reference characters. Turning now to FIGS. 1A-1C a method forassembling the battery of the present invention is illustrated. An arrayof conducting nanowires, 10, in electrical contact with conductingsubstrate, 12, is shown in FIG. 1A. Electrolyte material, 14, isconformal coated onto conducting nanowires 10, as shown in FIG. 1B.Cathode material, 16, in electrical connection with a second conductivematerial, 18, is interpenetrated between electrolyte-coated nanowires10, as shown in FIG. 1C, forming battery, 20.

Having generally described the invention, the following EXAMPLESprovides additional details:

Example 1 Anode Preparation

A. Cu₂Sb FILMS:

The direct electrodeposition of crystalline, stoichiometric Cu₂Sb filmsfrom aqueous solution at room temperature directly onto copperelectrodes at a single potential is first described.

Cu₂Sb films were electrodeposited from aqueous 0.4 M citric acidsolutions (denoted H₃Cit, 99.5+% Aldrich) containing 0.025 M antimony(III) oxide (Sb₂O₃, nanopowder, 99.9+% Aldrich), and 0.1 M copper (II)nitrate hemipentahydrate (Cu(NO₃)₂, 99.9+% Aldrich), prepared by addingthe citric acid to Millipore water (18Ω) followed by the addition ofSb₂O₃. The complete dissolution of the Sb₂O₃ was aided by mechanicalstirring after which the Cu(NO₃)₂ was added. The pH was then raised to 6by the addition of 5 M potassium hydroxide (KOH, ACS certified, Fisher).The Cu₂Sb films were obtained by performing bulk electrolysis at roomtemperature at a potential of −1050 mV versus a saturated sodium calomelelectrode (SSCE). The temperature and the potential were alsosystematically varied in order to find the optimal depositionconditions. Cyclic voltammograms (CVs) and depositions were conductedusing a three-electrode cell and a potentiostat. Platinum gauze was usedas a counter electrode, and a SSCE (0.236 V versus the standard hydrogenelectrode) was used as the reference electrode. A platinum diskelectrode (1.7 mm²) or a glassy carbon electrode (7.0 mm²) was used asthe working electrode for the CVs, and copper or gold flag electrodesfor the depositions. The copper flags were copper foil (0.25 mm thick,99.98% Aldrich) with an area of 2-4 cm², and were mechanically polishedusing diamond paste and electrochemically polished in phosphoric acid(H₃PO₄, 85%, Mallinkrodt Chemicals) at a current of 0.15 A for less than5 s. The gold substrates were made using a vacuum evaporator with adeposition controller. Approximately 10 nm of chromium was evaporatedonto glass slides as an adhesion layer, followed by 300 nm of gold.Electrical contact was made by connecting a copper wire to the flagswith carbon paint or with a clip. Clear nail polish was used to insulatethe edges of the substrate and the back of the copper foil in order toensure that deposition only occurred on flat surfaces with a controlledsurface area. The depositions were carried out at a constant potentialfor 10 min. periods. The films were rinsed with Millipore water andallowed to air dry.

Citric acid is a triprotic acid; therefore, solutions of varying pH wereexamined using cyclic voltammetry to study the effect of pH on thecopper and antimony deposition potentials. Solutions containingCu(NO₃)₂, Sb₂O₃, and citric acid were made ranging from pH 1 to 8. Theconcentrations of Cu²⁺ and Sb³⁺ were 0.1 M and 0.05 M, respectively(before the addition of KOH). Cyclic voltammograms (CVs) were taken frompH 1 to pH 8, inclusively, using 0.1 M Cu(NO₃)₂ and 0.025 M Sb₂O₃ (i.e.0.05 M Sb³⁺) in 0.4 M citric acid taken using a SSCE referenceelectrode, a platinum working electrode, and with a scan rate of 250mV/s.

In addition to significantly increasing the electrochemical window ofthe solution, raising the pH also controls which citrate species arepresent. Whereas at pH=1 the predominant species present for the citrateis the fully protonated species (denoted H₃Cit), at pH=6 there is amixture of HCit²⁻ and Cit³⁻. Once the electrochemical window is extendedtoward more negative potentials, the difference between the reductionpotentials of the metal species in solution is minimized at pH=6, whichpH has the additional advantage that slightly acidic pH conditionspreclude oxide precipitation during film deposition. A CV of the pH=6solution was found to exhibit a large cathodic peak at −950 mV, whichmay be attributed to the reduction of a copper citrate dimer, followedby a shoulder located at −1150 mV corresponding to the reduction ofSb³⁺.

The CV of citric acid alone exhibits two reduction peaks; one due to asurface phenomenon on Pt (at −118 mV) and one (at −750 mV) due to thereduction of a citrate species. As the pH is increased from 1 to 6, theCVs of each metal individually indicate that the Cu²⁺ reduction peakshifts in the negative direction while the Sb³⁺ reduction peak shifts inthe positive direction. Deposition at a single potential (−1050 mV)results in the formation of Cu₂Sb. Upon switching the scan direction, alarge oxidation peak is observed at 125 mV, corresponding to thestripping of Cu₂Sb. Only a single oxidation peak is observed, indicatingthat there is primarily a single oxidation process occurring at thispotential. Thus, copper metal is not deposited when Cu²⁺ alone iscomplexed by citrate at pH=6; however, in the presence of antimonycitrate two reduction peaks are observed with the result that Cu₂Sb isdeposited.

An effective concentration of citric acid for the deposition solutionwas determined by varying the concentration between 0.2-0.8 M, insolutions containing 0.05 M Sb³⁺ and 0.1 M Cu²⁺ separately. As theconcentration of citric acid was increased, the current of the coppercathodic peak decreased. This can be attributed to the equilibrium ofthe copper citrate complexes; that is, as more citric acid is added, theavailability of free copper ions in solution decreases. No difference inthe anodic or cathodic current was observed for the antimony solutions,although sufficient citric acid should be present to complex all theantimony in order to prevent the precipitation of Sb₂O₃. To avoid theprecipitation of Sb₂O₃, forming 0.05 M Sb³⁺ solutions, the minimumamount of citric acid needed was found to be about 0.4 M. Because lowerconcentrations of citric acid are desired for the copper deposition andat least 0.4 M citric acid is needed to keep Sb³⁺ in solution, 0.4 Mcitric acid was determined to be an effective citric acid concentration.All solutions used for subsequent discussions contain 0.1 M Cu(NO₃)₂,0.025 M Sb₂O₃, and 0.4 M citric acid adjusted to pH=6.

Using the solution conditions set forth hereinabove, an investigation ofthe deposition parameters was conducted. Films were deposited atdifferent potentials surrounding the cathodic peaks: the five potentialschosen were −800 mV (the onset of the first cathodic peak), −900 mV,−1000 mV (the first peak maximum), −1100 mV (the onset of the secondpeak), and −1200 mV. Compositional results determined by X-RayPhotoelectron Spectroscopy, XPS, show that the ratio of Cu/Sb decreaseswith more negative potentials. Relative to the desired 2/1copper/antimony ratio, copper-rich films are deposited at less negativepotentials, and antimony-rich films are deposited at more negativepotentials. The desired ratio was found for films deposited between−1000 and −1100 mV. This same trend was also observed in correspondingEnergy-Dispersive X-Ray Spectra, EDS data.

X-Ray diffraction (XRD) patterns were used for phase identification ofthe films deposited at various potentials using solutions containing 0.1M Cu(NO₃)₂, 0.025 M Sb₂O₃, and 0.4 M citric acid at pH=6. The Cusubstrate is responsible for the high intensity of three peaks at 43, 50and 74° 2θ, indexed to the copper (111), (200) and (220) reflections.Three additional peaks were observed in the XRD pattern of the filmdeposited at −800 mV. All three of these peaks match peaks for Cu₂Sb,one of which is generally used as the fingerprint for the desiredcompound (the broad (003) peak at 44° 2θ). The absence of additionalCu₂Sb peaks and the copper-rich composition determined by XPS indicatesthat this film is a mixture of Cu, Cu₂Sb, Sb and/or a solid solution ofCu and Sb. Multiple Cu₂Sb peaks appear in the XRD patterns of the filmsdeposited at all other potentials, indicating more crystalline films.The XRD patterns of the films deposited at −900 and −1000 mV aresimilar, but the peaks of the film deposited at −1000 mV have higherrelative peak intensities than the film deposited at −900 mV. Since allfilms were deposited for the same amount of time, the increased peakintensities may be due to increased crystallinity or simply greatergrowth rate. Although the Scanning Electron Microscope, SEM, images ofthese films also show similar surface morphologies, the film depositedat −900 mV shows larger features than the film deposited at −1000 mV.The grain sizes of the film deposited at −1000 mV are also smaller thanthe film deposited at −900 mV. As calculated by the Scherer method, thefilm grown at −900 mV is composed of grains that have an average size of90 nm, while the average size of the grains of the film deposited at−1000 mV is 35 nm.

The morphologies of the films deposited at −1100 and −1200 mV areconsistent with the differences between their XRD patterns and those ofthe films deposited at −900 and −1000 mV. An SEM image of the filmdeposited at −1100 mV, the pH=6 deposition solution containing 0.1 MCu(NO₃)₂, 0.025 M Sb₂O₃ and 0.4 M citric acid, shows dendritic growth.The observed diameter of the rods was found to range from 50 to 150 nmwith lengths greater than 600 nm. The average particle size calculatedfrom peak broadening was 50 nm, corresponding to the smallest observeddiameter from SEM. An SEM image of the film deposited at −1200 mV showssmall spherical particles (200 nm) on the surface of the film with acalculated grain size less than 20 nm. XRD patterns of films depositedfrom −1100 to −1200 mV can be indexed for Cu₂Sb and have the predictedrelative intensities. In addition, orientation is observed to be afunction of deposition potential: films deposited at potentials morenegative than −1100 mV have (111) orientation versus the films depositedat −900 and −1000 mV, which exhibit (001) orientation.

No differences in Cu₂Sb film composition were detectable by means of XPSfor films deposited from 5 to 60° C. The broadness of the XRD peaksdecreased with increasing temperature. Also, the surface morphology ofCu₂Sb films deposited at 60° C. exhibited cubic faceting.

The presence of oxide phases or amorphous inhomogeneities in theas-deposited films was investigated. A film for which an XRD wasrecorded was annealed for 5 h under argon at 220° C. The peak positionsobserved in both XRD patterns match except that small peaks observed inthe unannealed film are not present after annealing, which is consistentwith the removal of surface oxide phases.

All films discussed thus far were deposited in 10 min. periods fromunstirred solutions. Films having a thickness of 32.4 μm as determinedby SEM on a cross-sectional image show no discontinuities or pores in across-sectional view. Excluding any nucleation time, this corresponds toan average deposition rate of 3.24 μm per minute, compared to an averageof 0.72 μm per minute for the deposition of copper from a 0.2 M CuSO₄solution at a constant current of 10 mA. The observed rapid growth rateindicates that the solution parameters or interaction of the metalprecursors with the substrate may facilitate the electrodeposition ofCu₂Sb. To determine the importance of the substrate, films were alsodeposited on gold substrates. For these films the same solutionparameters and deposition conditions were used. A film deposited on Auwas slightly less crystalline than a film deposited on Cu, but stillexhibited a (001) orientation, implying that the observed preferredorientation for films deposited at −1050 mV is not a result oftemplating by the substrate.

Preliminary battery testing experiments on electrodeposited Cu₂Sb filmsshow that the as deposited films intercalate Li reversibly. All filmswere charged and discharged at a rate of C/3, (where C corresponds tothe rate needed to discharge an electrode in 1 h). The films were firstcharged between the open circuit potential (ocp) to a potential belowthat for depositing lithium metal (2 to 0.05 V vs. Li/Li⁺). To reducethe degradation of the solid electrolyte interface, the films were thenonly discharged to 1.2 V vs. Li/Li⁺. Subsequent cycles were run between1.2 and 0.05 V vs. Li/Li⁺. The consequences of the volume change (94%)that occurs during the change of Cu₂Sb to Li₃Sb were found to besignificant during the first charge. The active material was observed toslough off from the copper substrates, indicating that mechanicaldegradation due to self-pulverization is a significant source ofcapacity loss. All active material was found to be removed from thecopper substrate during the first ten cycles. A potential range of 1.4to 0.65 V vs. Li/Li⁺ was used to reduce the volume change (by 14%) byonly partially charging the film to Li₂CuSb. This improved the capacityof the material for the first 5 cycles, but the copper substrateappeared bare by the tenth cycle. The tested films were thick (32.4 μm)which may have caused the faster degradation.

The structural transformations of Mn₂Sb and MnSb are analogous to thatof Cu₂Sb during Li intercalation. In particular, MnSb has been shown todeliver a rechargeable capacity of 330 mAh/g. However, the lithiation ofMn₂Sb proceeds directly to Li₃Sb with very little LiMnSb formation, thencycles almost identically to MnSb, but with excess Mn present (asdetermined by in situ X-ray diffraction). Deposition of Mn₂Sb in amanner similar to Cu₂Sb was attempted. Analysis of CVs shows that as thepH is increased to 6 there is only a single distinct anodic peak present(at −1.2 V) due to the metal ions in solution (and not due to citricacid itself) before the onset of hydrogen evolution. Films deposited atpH=6 and −1.2 V indicate the codeposition of both metals, but not theintermetallic compound.

B. Pulsed Electrodeposition Of Cu₂Sb Nanowires:

Electrodeposition into templates (commercially available porous aluminaoxide and polycarbonate templates) has been used to synthesize variesmaterials on a nanoscale with a wide range of applications. One surfacethereof may be coated with a conducting metal such as gold using thermalevaporation, as an example, by first coating the surface with about 10nm of Cr followed by about 200 nm of Au to which is attached a copperwire using silver paint. Nanowire material may then be electrodepositedinto the pores, and the template dissolved leaving free-standing,well-ordered, equivalent-diameter nanowires. Removing the aluminatemplate was accomplished, using both sodium hydroxide (1 M) andphosphoric acid (3 M). As will be set forth hereinbelow, similartemplates may be used for creating nanowires of conducting metals suchas copper, gold, or platinum for use as templates for analysis ofelectrolyte deposition.

Electrodeposition of Cu₂Sb nanowires into porous alumina templates inaccordance with the film deposition technology described in part A ofthis EXAMPLE 1, at a single potential, resulted in non-uniform fillingof the pores, low density of filled pores and composition gradients overshort distances within the wires. By contrast, using the same solutionand potentiostatic pulse deposition, EDS spectral maps of the resultingwires exhibit a composition gradient which is uniform over largedistances.

FIG. 2 illustrates a sample square wave effective for the pulsedelectrodeposition of Cu₂Sb nanowires, where the deposition potential(E_(f)) was the same potential as used in the electrodeposition of films(−1.05 V versus SSCE). In pulse deposition (pulse plating), there aretwo time parameters which may be controlled: the on time (T_(on)) andthe off/reverse time (T_(off)). The concentration gradient establishedduring T_(on) dissipates during T_(off). This should allow for moreuniform wire growth and pore filling while limiting composition effectsthat are created by local concentration gradients established in thepores. The “quiet” potential (E_(r)), was varied to closely approachzero current, in order to stop the deposition for a sufficient length oftime for the concentration gradient to dissipate without oxidizingpreviously deposited material. In FIG. 2, T_(v) on the time axisrepresents the fact that T_(off) may be varied to obtain the desiredwire uniformity.

Preparation of the solutions for the pulse deposition of Cu₂Sb thinfilms and nanowires is described in part A, hereinabove. Allelectrochemistry was performed with a ±10 V potential range with a ±250mA current range and the ability to measure current on the tens ofpicoamperes; or with a ±2.4 V potential range and ±2 mA current rangewith the ability to measure current down to the 100 pA. Thepotentiostats were controlled using commercial software. Cyclicvoltammograms (CVs) and depositions were conducted using athree-electrode cell. The pulse sequence will be discussed in detail ina latter section. Platinum gauze was used as the counter electrode, anda SSCE (0.236 V versus the standard hydrogen electrode) was used as thereference electrode. A platinum disk electrode (2.01 mm²) was used asthe working electrode for the CVs, and the copper or gold electrodes forthe film depositions. The working electrodes for the film depositionwere either copper or gold evaporated onto glass slides. The substrateswere made using a vacuum evaporator with a deposition controller.Approximately 10 nm of chromium were evaporated onto glass slides as anadhesion layer, followed by 300 nm of copper or gold. Electrical contactwas made by connecting a copper wire with an alligator clip.

Using pulse potentiostatic deposition, films were deposited usingdifferent time constants (T_(on) & T_(off)) onto copper substrates. TheTABLE sets forth the parameters and summarizes the results. Both T_(on)and T_(off) are considerably longer than needed to charge the doublelayer, created by the externally applied voltage, which exists at theelectrode/electrolyte interface, and quickly dissipates. This allows anyeffects from charging of the double layer on the current orconcentration to be neglected. It may be observed from the data that thepotential found to give an approximately zero current was −0.525 Vversus SSCE, which corresponds to the region of the CVs between thereduction peaks and the oxidation peaks. Films deposited with shorterT_(on) times had diffraction peaks matching Cu_(3.3)Sb, while filmsdeposited with longer T_(on) times had diffraction peaks matching Cu₂Sb.Further, when the T_(off) time was varied keeping the T_(on) at 1.5 sthe crystallinity of the Cu₂Sb peaks increased with a decrease inT_(off).

TABLE Summary of parameters and results of pulse deposition of Cu₂Sbfilms onto copper substrates; each range corresponding to five differentvalues of the parameter. T_(on) T_(off) Examined Ms ms E_(r)-V E_(f)-VParameter Trend of Results 5-50 15-15000 −0.6 1.05 Pulse periodFormation of Cu_(3.3)Sb peak with long periods   5-50000  15-150000 0.181.05 Pulse period Peaks matched Cu₂Sb but with different orientations 150 1500 0.45-0.525 1.05 Dead The best powder pattern was obtained with−0.525 V potential 300-3000 1500 0.525 1.05 T_(on) Short T_(on) gaveCu_(3.3)Sb and long T_(on) gave Cu₂Sb 1500 150-7500  0.525 1.05 T_(off)Peaks matched Cu₂Sb with increased crystallinity with decreased T_(off)150-7500 75-3750  0.525 1.05 Pulse period Shorter period gave orientedcrystalline Cu₂Sb (001) The data show that with longer T_(on) times andshorter T_(off) times, the best X-ray diffraction (XRD) patterns areobtained; however, the crystallinity is much lower than the filmspreviously deposited using the unpulsed electrodeposition.

Example 2 Electrolyte Ipoly-[Zn(4-vinyl-4′-methyl-2,2′-bipyridine)₃](PF₆)₂

Electropolymerization is an effective method for creating conformalcoatings without pinhole defects on high-area electrodes for batteries.The control of the thickness of the polymer layer may create anelectrically resistive, ionically conducting barrier suitable foravoiding electrical shorts, inhomogeneous electric fields andinhomogeneous ionic diffusion rates. As will be described in thisEXAMPLE 2, the electropolymerization of poly-[Zn(4-vinyl-4′methyl-2,2′-bipyridine)₃](PF₆)₂ results in the conformal coating of highaspect ratio nanowire arrays without the presence of pinhole defects.[Zn(4-vinyl-4′ methyl-2,2′-bipyridine)₃](PF₆)₂ was chosen since: (a) thecomplex's metal-based oxidation, Zn^(+2/+3), requires a high potential,making it an alternative to the well-studied redox active ruthenium andosmium analogs; (b) the large electroinactive window of the polymerenables the separation of the electrodes to prevent shorting; and (c)the electropolymerization of the zinc tris(vbpy) complex is areduction-based polymerization achieved by applying a negative potentialto inject electrons into the bipyridine rings. The syntheses of theligand, 4-vinyl-4′ methyl-2,2′-bipyridine (vbpy) and the zinc tris(vbpy)analogue are known. In a potential cycling polymerization using thismaterial, the current response increases as polymer is deposited witheach cycle. It is also observed that Zn_((m)) plating onto the workingelectrode occurs when potentials more negative than ˜−1.70 V vs. SSCEare applied.

Atomic force microscopy, AFM, in contact mode was used to establish thethickness of the polymer films as a function of cycle number. Thicknesswas measured across scratches made in the polymer film with a razorblade. With a monomer concentration of 1 mM, and an electrode surfacearea of 0.1 cm², the thickness of the polymer film was found to varylinearly with cycle number up to twenty cycles. This correlation is notrigorous on nanowires due to the inherent differences in diffusionprofiles when depositing on nanowires versus a planar electrode;however, it is a useful guide for estimating the number of cycle numbersrequired to achieve an approximate thickness. Polymer coatings depositedon both films and nanowire arrays were examined.

Films were made by thermal evaporation, while copper nanowire arrayswere synthesized by electrodeposition of copper into porous anodicaluminum oxide (AAO). A thick layer of gold or copper was firstevaporated onto one side of an AAO template, a copper wire was attachedwith silver paint, and the entire metal surface on the back of the AAOwas painted with water insoluble, electrically insulating nail polish.Copper wires were then deposited in the AAO pores, and the aluminatemplate was selectively dissolved away, resulting in free-standingwires. Since the nail polish used is soluble in acetonitrile (thesolvent used in the electrochemical polymerization), in preparing thepolymer-coated nanowires, the electrodes were constructed by placing theAAO on a strip of conducting ITO glass (13Ω) and the surrounding ITOcovered with a non-conducting epoxy (TorrSeal) which is inert toacetonitrile. Scanning electron microscopy images of the copper wiresbefore and after polymerization exhibit a uniform change in morphologyfor the coated wires versus the as-deposited nanowires; that is, thenanowires were all uniformly thicker after the deposition process.However, imaging techniques are insensitive to low numbers of defects.

Redox shut-off experiments were conducted with similarly synthesizedplatinum nanowires since this technique should be sensitive to pinholesin the polymer coatings. Redox activity of two species having differentsizes and charges was investigated: the smaller, neutral ferroceneexhibits electroactivity on the polymer-coated electrodes, albeitsignificantly attenuated relative to each corresponding bare electrode,with a wave shape consistent with restricted diffusion ostensiblythrough the molecular-dimension pores of the polymer. By contrast, theredox activity of the larger, positively charged[Ru(2,2′,2″-terpyridine)₂]²⁺ species appears to be blocked on both theplanar and nanowire electrodes coated with polymer. Additionally, todetermine whether the polymer is acting as an ion exclusion layer, thevoltammetric response of cobaltocenium was also measured and found to besimilar to ferrocene. Electrochemical tests, coupled with the SEMmicrographs indicate that a conformal layer of poly-[Zn(4-vinyl-4′methyl-2,2′-bipyridine)₃](PF₆)₂ is deposited on the surface of thenanowires. A micrograph of the entire length of a polymer modifiedcopper nanowires, showed that the morphology and contrast is the samealong the entire length of the nanowires, indicating complete coverage.The same polymer has also been shown to grow on and adhere well tocopper, platinum, gold, and ITO surfaces. Therefore, it is expected thatthis polymer will deposit well on Cu₂Sb nanowires.

X-ray photoelectron spectroscopy (XPS) was used to further confirm thepresence of the polymer coating on both nanowires and films. Thepresence of the Zn 2p_(3/2) and F 1s peaks were used as the fingerprintsfor the presence of the polymer, and representative peaks for each metalwere probed on bare electrodes for comparison. Clear metal peaks areobserved before coating, and a complete lack of the metal peaks wereobserved for polymer coated nanowires and films. Finally, a series ofpolymer-modified patterned ITO electrodes were tested to examine thebreakdown voltage as a function of polymer thickness. A ˜30 nm polymerlayer electrodeposited on patterned ITO showed no appreciable currentflow up to its breakdown bias of ˜+3.5 V, which indicates that a thinpolymer layer is electrically resistive over a large voltage window.

A. Synthesis of 4-vinyl-4′-methyl-2,2′-bipyridine and[Zn(4-vinyl-4′-methyl-2,2′-bipyridine)₃](PF₆)₂

The syntheses of the ligand and the zinc complex were both taken fromliterature. The purity was checked using ¹H NMR before proceeding withelectropolymerization experiments.

B. Copper And Platinum Nanowire Generation

Porous Anodic Alumina (AAO) templates were obtained from Whatman (100 nmpores, 13 mm circles) and 3-5 nm of chromium followed by 1-1.5 μm ofcopper (or gold) was evaporated on one side as a back electrode.Electrical contact was made to the evaporated metal by attaching acopper wire with colloidal silver paint (Ted Pella—isopropanol based).Nanowires were deposited in a three electrode cell, with a SSCEreference electrode, a platinum mesh counter electrode and the AAOworking electrode. For copper, the 10 ml reaction solution consisted of0.627 M CuSO₄ in 18Ω (Millipore) H₂O and 1 ml of concentrated H₂SO₄. TheAAO working electrode was submerged in the reaction solution until theopen-circuit potential (E_(oc)) remained constant over 5 min. Thepotential was held at 0.3 V below the E_(oc) for 450 s to yield coppernanowires ˜5 μm in length and 100 nm in diameter. The solution wasstirred during the deposition (˜100 rpm) to replenish reactants to thepores of the AAO template. Platinum nanowires were prepared in a similarmanner, only the 10 ml deposition solution used was a 0.01 M H₂PtCl₆solution with 1 ml of HClO₄ (70 wt %). The potential was cycled between+0.463 V and −0.237 V (vs. SSCE) at 0.05 V s⁻¹ for 60 cycles to yieldplatinum nanowires that were ˜3.5 μm long and 100 nm in diameter.

C. Nanowire Electrode Fabrication

Once the nanowires were grown, the templates were removed from solutionand thoroughly washed with distilled water and ethanol. The conductingback of the AAO electrode was then attached to the conducting side ofITO glass with water-based colloidal graphite (Aquadag, Ted Pella) anddried in vacuo for 2 h. Once dried, epoxy (TorrSeal), chemically inertin CH₃CN solutions, was used to cover both the AAO template and the ITOconducting glass so that only ˜1 cm² area of the template was exposed.The epoxy was then left to dry in open air for 24 h, after which theelectrode was immersed in aqueous 1 M NaOH at 50° C. for 1 h to releasethe nanowires. Copper and platinum nanowire electrodes were bothsynthesized in this manner.

D. Electropolymerization of [Zn(4-vinyl-4′methyl-2,2′-bipyridine)₃](PF₆)₂

Electropolymerization was achieved by utilizing a three-electrode VanDyne cell where all oxygen was evacuated by bubblingacetonitrile-saturated nitrogen through the 0.1 M TBAPF₆/CH₃CN beforepolymerization. Additionally nitrogen was blown over the cell tominimize oxygen contamination. Oxygen evacuation was confirmed by takinga background cyclic voltamogramm between 0 V and −1.2 V vs. SSCE. In allcases, a platinum wire was used as a counter electrode and the referenceelectrode was a saturated sodium calomel electrode (SSCE). Allelectrochemical and solid-state electrical measurements were done on aCH Instruments 650 potentiostat/galvanostat.

E. Solid-State Linear Sweep Voltammetry

Electrical measurements performed on a nanometer thick layers wereadapted from methods found in the literature. A Ga—In liquid metaleutectic (Sigma-Aldrich, used as received) was used to make contact tothe bare and polymer covered ITO. Tungsten wire, pre-wetted by immersioninto the Ga—In eutectic for 30 s, was then used to contact the liquidmetal on the surface of the electrode. All solid-state electricalmeasurements were done in an N₂-filled glove-box and the bare ITO waspositively biased.

F. Physical Characterization of Polymer Thin-Films, Nanowires andPolymer-Modified Nanowires

Scanning electron microscopy (SEM) was utilized to characterize thenanowires, before and after polymer modification. The acceleratingvoltage of the electron beam was lowered to 3 keV during imaging ofpolymer films due to excessive charging of the non-conducting polymer.X-ray photoelectron spectroscopy (XPS) (Phi 6500) was used tocharacterize the surface of the different electrodes. Measurements wereperformed with an Electron Spectrometer for Chemical Analysis system andanalyzed using commercial software. An Al monochromatic source operatingat 350.0 W was scanned at an energy of 58.7 eV in intervals of 0.125 eVstep⁻¹ over the range indicated on the spectra. High resolution XPS wasperformed using a signal to noise ratio of at least 100:1 for the filmsand 50:1 for the nanowires. The thickness and topography of the polymerfilms were analyzed using atomic force microscopy (AFM) (Alpha NSOM withcontact mode capabilities) of the as deposited films on etched ITOsubstrates. Analysis of the topography was achieved on an 100 μm×100 μmarea, and the height was determined using the scratch method: A cleanrazor was used to scratch through the polymer film to the ITO substrateand a depth profile of the scratch was taken from two scratches on threeseparate electrodes to yield the mean thickness and error.

G. “Redox Shut-Off” Experiments

The complexes [Ru(2,2′,2″-terpyridine)₂](PF₆)₂,[Co(cyclopentadienyl)₂](PF₆) and [Fe(cyclopentadienyl)₂] (Aldrich, usedas received) were used to make a 10 mM solution in 0.1 M TBAPF₆\CH₃CN.The three electrode cell was comprised of a platinum mesh counterelectrode, Ag/AgCl reference, and the stated working electrode. CyclicVoltamogramms were taken at 0.05 Vs⁻¹.

Example 3 Electrolyte II Acrylates

The polymer films disclosed herein are useful as solid-state electrolytematerials for use in electrochemical cells, such as lithium-ionbatteries. This is largely due to their high ionic conductivity and lowelectronic conductivity. These films are particularly useful inbatteries with very small scale features (such as nanoscale) becausethey can be conformally deposited using an electroreductivepolymerization method. This method results in good uniformity of filmthickness without large numbers of pinholes and other defects, makingthe film of sufficient quality that the film is suitable for applicationas an electrolyte in a lithium-ion battery.

Reductive electropolymerization is well-known in the art, including thereductive polymerization of vinyl monomers. The first step infabricating the films disclosed herein is to electrochemically reduce avinyl monomer, in particular an acrylate-based monomer (includingmethacrylates, methacrylic acid, acrylic acid, acrylamide,methacrylamide, vinyl acetate and related), and specificallytetramethylammonium 3-sulfopropyl acrylate (TPASPP), lithium3-sulfopropyl acrylate (LiSPP), and glycidal methacrylate (GYM). Anadvantage of GYM is that it contains heteroatoms (namely oxygen) thatcan assist in the conduction of lithium ions. An advantage of SPP-basedfilms is that the presence of a covalently bound anion can assist in theconduction of lithium cations by virtue of offering acharge-compensating anion.

Electrochemical reduction of these monomers, under the appropriateconditions (e.g. supporting electrolyte, solvent, counter/auxiliaryelectrode, oxygen-free environment), will initiate the polymerization ofthese monomers. As radical propagation continues, a solid film will bedeposited on the surface of the electrode as the polymer chain grows.The specific conditions employed may be used to determine the propertiesof the film (e.g. thickness, uniformity). Common techniques includestepping to a defined voltage and potentiometric cycling of theelectrode. Reductive electropolymerization permits conformal depositionof polymeric films of controlled and generally uniform thickness onto anelectrode surface with morphological features of either very small size(for example, nanoscale dimensions) and/or irregular or complexpatterning. For batteries and other electrochemical cells, thistechnique may be used to generate films on nanowires, nanotubes, andrelated nanostructures which have been previously fabricated on theelectrode surface (for example, Cu₂Sb nanowires), when the electrolyteis required to be thin and conformal so that the battery cathodematerial can be deposited in and among the nanowires.

Once the film has been deposited, a “Li⁺ doping” after treatment may berequired to enable sufficient ionic conduction and to introduce lithiumion into the system. It is believed that the ionic conduction of polyGYMderives from etheral oxygens having a slight negative charge sufficientto attract Li⁺ (similar to PEO doping). It has been observed by theinventors that when polyGYM is soaked in 1M LiClO₄ (in propylenecarbonate, or PC) for 48 h, dip-rinsed, and the PC removed in vacuo at˜70° C., the polymer may be doped to form LiClO₄: polyGYM, as may becorroborated using high-resolution XPS. In the case of the SPP polymer,any film produced from monomers with cations other than lithium mayrequire a cation exchange procedure (e.g. exchanging K⁺ for Li⁺, or TMA⁺for Li⁺). Cation exchange is a technique well-known to those skilled inthe art and may be accomplished in a number of ways, for example, thesoaking procedure described above for polyGYM, perhaps repeated two ormore times, would be expected to result in successfully ion exchange.

Acrylates are well known to deposit onto any electrically conductivesurface. Therefore, the acrylates should readily deposit onto Cu₂Sb.

Example 4 Cathode Materials

Materials found useful for large-scale lithium batteries includinglithium cobalt oxide, lithium magnesium oxide, or lithium tin oxide, areexpected to be effective for the present lithium ion battery. Althougheach of these materials has a theoretical capacity, the actualcapacities of the bulk materials are much smaller (110 for cobalt, 150for manganese, and 270 for tin). The capacities are expected to begreater when used on a nanoscale due to a higher surface area to volumeratio, and the greater ability of the nanowires to withstand the volumeexpansion and contraction that results in pulverization of the bulkmaterials. These materials were synthesized using a sol gel method inalumina templates. Such methods begin with dissolving precursors insolution. The space between the coated nanowires in the batterystructure is filled with the solution. A slow reaction forming a soloccurs, the sol densifying in time to form a gel. Alcohol may be addedto the solution, the ratio of water to alcohol in the initial solutionbeing useful for controlling the gelation time of the sol. The gel isannealed at a chosen temperature to generate a powder which uniformlycoats the nanowires. The second electrode may then be placed inelectrical contact with the powder by a number of well-known methods,such as thermal evaporation of a metallic species, as an example. Thethickness of the cathode material may be matched to the amount oflithium in the anode material.

1. Lithium cobalt oxide (LiCoO₂):

Equal molar quantities of lithium acetate (Aldrich, 99.99%) and cobalt(II) acetate (Aldrich, 98%) were mixed in a 4:1 molar solution ofEthylene glycol (Fisher Scientific, lab grade) and citric acid(Sigma-Aldrich, analytical grade). The solution was then heated to 140°C. for 5 h while stirring, until a pink gel was formed, to induceesterification, and then left to cool. The solution may be poured ontothe nanorods or the nanorods may be dipped into the solution as it isbecoming a gel over time, followed by a low-temperature anneal. Thepowdered materials may then be generated by heating the annealed gel tohigher temperatures. Samples were prepared either on glass slides or on100 nm sized porous alumina templates (Whatman Filters, anodisc 13, 0.1μm) and placed in a vacuum at 60° C. for 1 h. For the templates thisprocess was repeated multiple times to ensure proper filling of thepores. The samples were then placed in the oven and heated for 16 h to550° C. with an increase in temperature of 0.3 to 1° C. per min. Porousalumina templates were employed to simulate high-aspect ratiostructures, such as nanowires. At temperatures below 500° C. thepink/red samples created a glass like phase in which no powder wasobtained; above 550° C., powders effective for use as cathode materialswere generated.

2. Lithium manganese oxide ((LiMnO₂ FCC, Li_(0.82)[Mn_(1.7)Li_(0.3)]O₄monoclinic)):

Lithium manganese oxide was prepared in the same manner except thatmanganese (II) acetate (Aldrich, 98%) replaced the cobalt acetate.Samples were obtained on glass slides for the lithium manganese oxidegel. At temperatures below 200° C. the brown samples created a glasslike phase in which no powder was obtained.

3. Lithium tin oxide (Li₂SnO₃):

Lithium tin oxide was prepared in the same manner except that tin (II)chloride (Sigma Aldrich, reagent grade) replaced the cobalt acetate.Samples were obtained on glass slides for the lithium tin oxide gel, alltemperatures producing a white powder.

Phosphates such as LiFePO₄, as an example, may also be used, which mayexhibit higher voltages and longer lifetimes than typical oxides. Thelithium ferrous phosphate may be doped with cobalt, aluminum ormagnesium.

The foregoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed, andobviously many modifications and variations are possible in light of theabove teaching. The embodiments were chosen and described in order tobest explain the principles of the invention and its practicalapplication to thereby enable others skilled in the art to best utilizethe invention in various embodiments and with various modifications asare suited to the particular use contemplated. It is intended that thescope of the invention be defined by the claims appended hereto.

1-40. (canceled)
 41. A method for electrodepositing copper antimonideonto an electrically conducting substrate, comprising: preparing asolution having a chosen molar concentration of Cu⁺² and a chosen molarconcentration of Sb⁺³ in an aqueous solution of having sufficient citricacid present such that precipitation of the Sb⁺³ does not occur;increasing the pH of the solution such that a mixture of HCit²⁻ andCit³⁻ species is formed from the citric acid, and the difference betweenthe reduction potential of the Sb⁺³ to Sb and the reduction potential ofCu⁺² to Cu is minimized; applying a chosen negative potential to theelectrically conducting substrate; whereby Cu₂Sb is electrodepositedonto the substrate.
 42. The method of claim 41, wherein the chosen molarconcentration of Cu⁺² is twice the chosen molar concentration of Sb⁺³.43. The method of claim 41, wherein the concentration of citric acid ischosen to be the minimum concentration that will ensure dissolution ofSb⁺³.
 44. The method of claim 41, wherein the chosen negative potentialis between about −0.8 V and about −1.2 V verses a saturated sodiumcalomel electrode.
 45. The method of claim 44, wherein the chosennegative potential is approximately −1.05 V verses a saturated sodiumcalomel electrode.
 46. The method of claim 41, wherein the chosennegative potential is continuously applied.
 47. The method of claim 46,wherein the chosen negative potential is applied until a chosen mass ofcopper antimonide is deposited onto the substrate.
 48. The method ofclaim 46, wherein the chosen negative potential is constant during theelectrodeposition.
 49. The method of claim 41, wherein the Sb⁺³ isobtained from dissolution of Sb₂O₃.
 50. The method of claim 41, whereinthe Cu⁺² is obtained from dissolution of Cu(NO₃)₂.
 51. The method ofclaim 41, wherein the chosen molar concentration of Sb⁺³ isapproximately 0.05 M.
 52. The method of claim 51, wherein the chosenconcentration of citric acid is between about 0.2 M and about 0.8 M. 53.The method of claim 52, wherein the chosen concentration of citric acidis about 0.4 M.
 54. The method of claim 51, wherein the pH of thesolution is approximately
 6. 55. The method of claim 41, wherein theelectrically conducting substrate has a surface comprising complexshapes.
 56. The method of claim 41 wherein the Cu₂Sb is electrodepositedin the absence of a post-electrodeposition annealing step.
 57. Themethod of claim 41, wherein the chosen negative potential is pulsedduring the electrodeposition.
 58. The method of claim 57, whereinduration and duty cycle of the pulses are separately controlled.
 59. Themethod of claim 58, wherein the pulse duration is between about 5 ms andabout 50,000 ms.
 60. The method of claim 58, wherein the duty cycle ofthe pulses is between about 1% and about 99%.